Vale's carriers were barred from China from Jan. 2012 to Sept. last year, due to rules preventing ships of more than 250,000 dwt in capacity from docking at mainland ports.

In February, Beijing finally amended rules around vessels allowed to berth at its harbors, paving the way for the entry of Vale's giant ships, known as Valemaxes, which can carry up to 400,000 deadweight tons.

Vale's inability to dock its iron ore carriers at Chinese ports had stymied its efforts to reduce freight costs and to compete with Australian based-rivals like BHP Billiton (ASX:BHP) and Rio Tinto (LON:RIO), which are closer to China.

If the shipbuilding deal rumor were confirmed, the order would be the largest in history for this kind of massive ore carriers.